1. Field of the Invention
The present invention relates to an IC (Integrated circuit) including a transistor having a gate insulation film.
2. Description of the Related Art
A silicon nitride film (SiN film) has been widely used as a passivation film or interlayer insulation film of an IC.
In a transistor having a gate insulation film, an interfacial level of a gate insulation film is shifted if hot carriers enter the gate insulating film. As a result, hot carrier deterioration that the gate insulating film fails to function properly may occur.
When a plasma SiN film is used as, for example, a passivation film in a transistor having a gate insulation film, the hydrogen contained therein also enters the gate insulation film and promotes the hot carrier deterioration (The Technical Studies Reports At The Electronic Data Communication Learned Society 90-123, p 33, "Hot Carrier Effects" by Kenichiro TATSUUMA and others). When the amount of hydrogen in a passivation film is decreased as a countermeasure against the above-described problem, a film stress of the passivation film increases. As a result, there arises the problem that the generation of Al (aluminums voids and the like follows. Here, the aluminum is used as wiring in a transistor. Also, when it is attempted to achieve the decrease in the film stress by reducing a flow rate of gas to form a passivation film and thereby lower the density thereof, the coverability of the passivation film deteriorates particularly at a stepped portion. In addition, the amount of hydrogen contained in the passivation film is likely to increase. As a result, there may arise problems with respect to the moisture resistance of the passivation film as well as the hot carrier deterioration. In this way, it is impossible to achieve the enhancement of a hot carrier life while satisfying sufficiently the moisture resistance, low film stress, uniformity of the film thickness which becomes important in manufacture, and producibility as originally designed which are needed in a protective film. Further, if a semiconductor device is a memory device such as an EPROM, UV, transmission characteristic and charge retention characteristic of a floating gate become important factors to the protective film.
For the above-mentioned reasons, it has been demanded to provide a semiconductor device which can excellently enhance the hot carrier life while ensuring the UV transmission characteristic and charge retention characteristic as well as the moisture resistance (enhanced stepped portion coverage) and decreased film stress without changing a basic film thickness. Further, when such a semiconductor device is realized, a change in the film forming conditions made with respect to the conventional manufacturing method should avoid resulting in a decrease in a throughput and an increase in a manufacturing cost.